Abstract. Dorothia and Marssonella are ataxophragmiacean genera typically possessing canaliculate walls. They are believed to have evolved independently from noncanaliculate Praedorothia gen. nov. and Protomarssonella gen. nov. of Early Cretaceous time.
Abstract. The early, coiled stages of Orbulina suturalis and O.universa are described from both Middle Miocene (zones N9–N12) and Quaternary samples. The coiling mode of Orbulina is unique to that genus, and has remained unchanged (as have the spines characteristic of the coiled growth stage) since that genus and its species first evolved. Orbulina universa is monophyletic and its evolutionary history appears to provide an example of “punctuated equilibria” in the development of Cainozoic Globigerinacean development. “O. suturalis “, on the other hand, appears to be a name which has been applied both to the Middle Miocene species and to phylogenetically different forms of Quaternary age.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.